The present invention relates to an engine starting system for an internal combustion engine. More particularly, the invention relates to an automatic choke system for a small engine.
Internal combustion engines often include a system or mechanism to regulate the air/fuel mixture to the engine based on engine temperature conditions. A choke valve typically regulates the airflow to the engine. For cold engine temperature conditions, such as when initially starting an engine, the choke valve reduces the airflow to the engine to enrich the air/fuel mixture. For higher temperature conditions, such as after normal engine operation (e.g. for a hot restart of the engine), the choke valve is not needed because the engine no longer requires a rich air/fuel mixture.
In one embodiment, the invention provides an engine starting system that includes a battery, a starter motor, a starter switch, a solenoid actuator, a choke valve, and a temperature switch. The starter switch is electrically connected between the battery and the starter motor for the engine. The choke valve is disposed in an air intake of an air/fuel-mixing device for the engine. The choke valve interconnects with and moves in response to the solenoid actuator. The solenoid actuator is electrically connected to the starter switch and the temperature switch. Above a certain threshold temperature, the temperature switch interrupts the power supplied to the solenoid actuator. If the power to the solenoid is interrupted, a bias spring connected to the solenoid actuator moves the choke valve to an open position.
In another embodiment, the engine starting system further includes a time delay electrically connected to the solenoid. The time delay energizes the solenoid actuator for an extended period of time after the starter switch closes. In yet another embodiment, the engine starting system further includes a free wheeling diode electrically connected between the positive and negative terminals of the solenoid actuator. After electrical power is interrupted to the solenoid actuator, the free wheeling diode re-circulates and dissipates the electrical current of the solenoid actuator.
In a small engine application, the invention regulates the air intake of an air/fuel-mixing device based on starter motor activation and temperature conditions. Electrically connecting a solenoid actuator between a temperature switch and starter switch provides an economical means for regulating the open position of a choke valve when powering a starter motor at hot versus cold temperatures.